Studies on NS the Phosphoprotein of Vesicular Stomatitis Virus

Abstract

<p>The vesicular stomatitis virus phosphoprotein, NS, was the subject of this investigation. Multiple forms of NS protein were identified in Piry infected cells. These multiple species were demonstrated to be related by comparative peptide mapping under conditions of complete or partial digestion. Furthermore, kinetic studies revealed that one of the NS forms (NSᵢ) could be converted into a mature NS form (NSᵥ) by a covalent post-translational modification. The nature of this modification was investigated using inhibitors of both phosphorylation and acetylation.</p> <p>NS protein isolated from cells infected with the Indiana serotype was structurally characterized by a variety of techniques including enzymatic digestion, chemical cleavage and partial acid hydrolysis. The observations presented here indicate that NS exists under denaturing conditions as a monomer and is post-translationally modified by multisite phosphorylation. NS isolated from infected cells appears to be phosphorylated toward the amino terminus of the polypeptide primarily in one large tryptic peptide.</p> <p>Monospecific antisera were raised against SDS-polyacrylamide gel purified Indiana virion proteins. These sera were used to investigate viral protein aggregates in both virions and infected cells. In particular it was demonstrated that a protein kinase activity capable of in vitro phosphorylation of NS protein could be identified in immunoprecipitates of NS protein.</p> <p>The significance of these findings with respect to other published observations is discussed.</p>